Canine IL-17A (Interleukin-17A) is a pro-inflammatory cytokine belonging to the IL-17 family that plays a central role in host defense and inflammatory responses in dogs (Canis lupus familiaris). IL-17A is produced primarily by Th17 cells, as well as by γδ T cells and other innate lymphoid cell populations, in response to microbial infection and inflammatory stimulation. It acts on epithelial, endothelial, and stromal cells to induce the expression of pro-inflammatory cytokines, chemokines (such as CXCL8), and antimicrobial peptides, thereby promoting neutrophil recruitment and enhancing mucosal and barrier immunity. In healthy dogs, basal IL-17A expression is typically low, but levels increase during bacterial and fungal infections, chronic inflammatory conditions, and immune-mediated diseases. Elevated IL-17A has been implicated in canine atopic dermatitis, inflammatory bowel disease, immune-mediated polyarthritis, chronic rhinitis, and certain autoimmune or inflammatory neurologic disorders. In veterinary and comparative medicine research, canine IL-17A serves as an important biomarker of Th17-mediated immune activation and neutrophilic inflammation, providing insight into disease pathogenesis and potential immunomodulatory therapeutic strategies in canine health.